Perhaps Naruto discovers a hidden connection between the Senju and Uchiha that has been lost over time. This could lead him on a journey to uncover the truth about their past relationship and how it might impact the future of the ninja villages. It could also involve him uniting the remaining members of both clans in a new alliance.
One interesting aspect could be Naruto's identity crisis. He is known as Uzumaki Naruto, but now being related to Uchiha and Senju, he has to re - evaluate who he is. He might struggle with the expectations that come with these powerful lineages. And his role in the village could change significantly as he represents two of the most important clans in the ninja world.
He would likely become more powerful. With Uchiha and Senju blood, he could access new levels of chakra and skills. For example, he might be able to use the Susanoo more effectively than other Uchiha. His character might also become more complex, as he has to balance the different traits of the two clans.
The Uchiha might initially be filled with anger. Their trust in Naruto, if it was there before, would be completely shattered. They could start to plot revenge against Naruto, believing that he has wronged them. This could lead to a lot of tense moments in the fanfiction as the Uchiha gather their strength and resources.
It makes him more complex. Instead of just having his Uzumaki heritage, he now has to deal with the traits and expectations of the Senju and Uchiha. He might become more introspective as he tries to understand the differences and similarities between the three lineages.
You should check out 'Naruto & Sasuke: Partners in a New World'. This fanfic takes the two characters and places them in a different, more modern - day like setting while still maintaining their core personalities. It's a fresh take on their relationship. And 'Sasuke's Return to Konoha' is a fanfic that focuses on Sasuke coming back to the village and how he and Naruto work together to improve the village and their standing in it. It has some great dialogue between the two.
One possible storyline could be Naruto exploring his new abilities. He might have to train hard to control the powers from both bloodlines. Another could be that other clans become either jealous or fearful of him. There could also be a storyline where Naruto uses his combined DNA to bridge the gap between the Senju and Uchiha, who have a long - standing rivalry.
Their relationship could start off rocky. Naruto Senju might be too brash and Fem Sasuke too reserved. But as they face challenges together, they start to understand each other. For example, when they are on a mission to rescue a group of hostages, Naruto Senju's bold moves might initially annoy Fem Sasuke. But then she realizes his courage is an asset.
Perhaps a plot where Naruto Senju and Fem Sasuke are in a world where the ninja villages are at war again. They have to use their skills and intelligence to broker peace. Fem Sasuke's Sharingan and Naruto Senju's Wood - Style techniques could be used in creative ways to outwit their enemies and bring about diplomatic solutions.